Background: Early childhood is a period of rapid brain development characterized by profound changes in grey matter morphometry. Brain injury occurring during this period may impact child brain development differently than in older pediatric groups, with possible long lasting consequences on child functioning. Pediatric traumatic brain injury (TBI) has been associated with regional grey matter atrophy (Mayer et al., 2015; Ryan et al., 2016). Children included in the studies conducted so far mostly sustained TBI after the age of 10 years. Thus, while TBI is particularly prevalent in children younger than 6 years, the impact of TBI on the brain structure of very young children is still poorly understood. The aim of the present case series was to investigate grey matter brain structure in the very long-term after TBI before the age of 4 years. Method: Two adolescents (mean age: 14.6y) who sustained a severe TBI at 39 and 45 months of age (early-TBI), 10 adolescents (mean age: 16.6y) who sustained a severe TBI between 9.7 and 15.2 years of age (adolescent-TBI group; mean age at injury: 13.2y), and 15 adolescents (mean age: 15.8y) with no history of brain injury (no-TBI group) underwent magnetic resonance imaging (MRI). Processing of structural images (T1-weighted) was performed in SPM12. W-scores (i.e., age and sex-adjusted Z-scores) were calculated voxel-to-voxel to compare the two early-TBI participants with both the adolescent-TBI and the no-TBI groups. W-scores inform on the difference between the observed value of one participant and the expected value in the comparison group for the participant’s age and sex. W-scores were thresholded at 2.33 corresponding to a p-value of .01. Results: The two early-TBI participants had significantly more grey matter volume in the temporal gyrus (inferior, superior and pole) than both those in the adolescent-TBI and in the no-TBI groups. Discussion: Although limited to two cases, the present study provides rare evidence that early TBI may be associated with long-lasting changes in temporal grey matter volume. Children who sustain severe TBI during early childhood show greater grey matter volume in the temporal gyrus more than 10 years post-injury, compared with children who sustain TBI in later childhood/adolescence or who are uninjured. In contrast, severe TBI sustained during adolescence has been associated with volumetric reductions in regions of the social brain network that include the temporal gyrus (Ryan et al., 2016). Early and late pediatric TBI may differentially impact the developing brain, possibly depending on the developmental stage of brain maturation (i.e., synaptogenesis at earlier ages vs. synaptic pruning at later ages).

Early childhood severe traumatic brain injury is associated with long-lasting changes in temporal grey matter volume: A case series